1. Field of the Invention
The present invention relates to an organic EL device and a method for manufacturing the same.
2. Description of Related Art
Organic EL devices are recently used in various industrial fields, for example, a back light device of a liquid crystal display (LCD) device, a portable terminal apparatus, an automobile navigator and a computer, a television, because of its rapid response speed, excellent brightness, simple structure, low production cost, light weight, etc.
The organic EL device includes first electrodes or anode electrodes formed on a substrate and second electrodes or cathode electrodes with light-emitting layers interposed therebetween.
A method for manufacturing such an organic EL device is as follows. First, an indium-tin oxide (ITO) film is formed all over a front surface of a glass substrate in a vacuum atmosphere. Then, the ITO film is formed into a stripe-like shape by etching, resulting in a plurality of transparent electrodes or first electrodes arranged side by side and spaced from each other at predetermined intervals. Then, the light-emitting layer is formed on the first electrode. The light-emitting layer includes a hole transport layer, a luminescent layer, and an electron transport layer, which are laminated in sequence and sandwiched between an anode and a cathode.
In more detail, the hole transport layer, which is made of a hole transport material such as a triphenylamine derivative (TPD) or the like, is formed on the transparent electrodes by vacuum deposition. Subsequently, a layer made of an electron transport material such as an aluminum quinolinol complex (Alq3) acting as a luminous material is laminated on the hole transport layer, resulting in a luminous material layer being formed by vacuum deposition. Then, material like Al, Li, Ag, Mg, In is deposited in a stripe-like manner on the luminous material layer so as to extend in a direction perpendicular to a pattern of the transparent electrodes, thereby provide a plurality of rear electrodes or second electrodes. In such a construction, portions of the luminous material layer positioned at intersections between the transparent electrodes and the rear electrodes define luminous sections, resulting in forming a dot matrix. The organic EL device operates by flowing a current to the luminous sections positioned on the intersections between the transparent electrodes acting as anodes and the rear electrodes acting as cathodes, illuminating the luminous sections.
However, the organic EL device having such a configuration has a problem of very low contrast ratio because ambient light is reflected from the second electrode made of a metal and lowers brightness. In order to clearly observe displayed images under a condition of a standard illuminance, i.e., 500 lux, a contrast ratio of at least eight to one (8:1) is required. However, ambient light reflected from the cathode electrode is directed toward an observer. Therefore, a contrast ratio is lowered to less than eight to one, leading to a very low brightness enough not to clearly recognize displayed images.
In order to overcome the problem described above, a circular polarizer is arranged either of on a top surface and a bottom surface of the anode electrode. However, the circular polarizer lowers a transmittance of light emitted from the light-emitting layer to be less than about 50%. As a result, a brightness of the organic EL device is decreased as much as about 50%. In order to improve this low brightness problem, electrical current should be doubled because a light intensity is proportional to a current intensity. However, such an approach increases power consumption. Considering that most of the organic EL device is portable, large power consumption causes an inconvenience to users. In addition, a life span of the organic EL device is in inverse proportion to an intensity of electrical current applied. Therefore, applying more electric current shortens the life span of the organic EL device. Also, an addition of the circular polarizer also increases production costs.
Meanwhile, the anode electrode is made of indium tin oxide (ITO) and thus has relatively high resistance value of 10xcx9c20xcexa9. Therefore, a current loss is relatively high. Recently, in order to overcome the problem, a technique is introduced that an auxiliary electrode made of relatively low resistive metal is arranged along an edge of the ITO layer without affecting the display characteristics. However, this technique also has a problem that additional processes to form the auxiliary electrode are required, leading to a lengthy manufacturing process.
It is an object of the present invention to provide an organic EL device having a high brightness.
It is another object of the present invention to provide an organic EL device having low power consumption.
It is a still further object of the present invention to provide an organic EL device having a lengthy life span.
It is also a still further object of the present invention to provide an organic EL device having an excellent productivity.
It is also a still further object of the present invention to provide an organic EL device having a simplified manufacturing process.
In order to achieve the above object, the preferred embodiments of the present invention provide an organic EL device, including first electrodes formed on a transparent substrate and spaced apart from and parallel to each other"" a light absorbing layer having an opening portion for exposing a portion of the first electrodes and at least one light absorbing piece arranged in the opening portion, light-emitting layers formed on the exposed portion of the first electrodes to cover the opening portion of the light absorbing layer, and second electrodes formed on the light-emitting layers in a perpendicular direction to the first electrodes.
The preferred embodiment of the present invention provides an organic EL device, including a transparent substrate, a light absorbing layer having a first opening portion and at least one light absorbing piece arranged in the opening portion, first electrodes covering the opening portion of the light absorbing layer and parallely spaced apart from to each other an insulating layer having a second opening portion formed at a location corresponding to the first opening portion of the light absorbing layer and at least one insulating piece formed at a location corresponding to the light absorbing piece, light-emitting layers formed on the exposed portion of the first electrodes to cover the second opening portion, and second electrodes formed on the light-emitting layer in a perpendicular direction to the first electrodes.
The preferred embodiment of the present invention provides an organic EL device, including first electrodes formed on a top surface of a first transparent substrate spaced apart from and parallel to each other, an insulating layer having a first opening portion for exposing a portion of the first electrodes and at least one insulating piece formed in the first opening portion, light-emitting layers formed on the exposed portion of the first electrodes to cover the first opening portion of the insulating layer, second electrodes formed on the light-emitting layer in a perpendicular direction to the first electrodes, and a light absorbing unit attached on a bottom surface of the transparent substrate and having a second opening portion formed at a location corresponding to the first opening portion of the insulating layer and at least one light absorbing piece formed at a location corresponding to the insulating piece of the insulating layer.
The preferred embodiment of the present invention provides a method for manufacturing an organic EL device, including steps forming on a transparent substrate first electrodes spaced apart from and parallel to each other, forming a light absorbing layer having an opening portion for exposing a portion of the first electrodes and at least one light absorbing piece arranged in the opening portion, forming light-emitting layers on the exposed portion of the first electrodes to cover the opening portion of the light absorbing layer, and forming second electrodes on the light-emitting layers in a perpendicular direction to the first electrodes 23. The method may further comprise a step of forming a metal layer on one side of the first electrodes and in a longitudinal direction of the first electrodes before the step of forming the light absorbing layer.
The preferred embodiment of the present invention provides a method for manufacturing an organic EL device, including forming a transparent substrate, forming a light absorbing layer having a first opening portion and at least one light absorbing piece arranged in the opening portion, forming first electrodes spaced apart from and parallel to each other for covering the opening portion of the light absorbing layer, forming an insulating layer having a second opening portion arranged at a location corresponding to the first opening portion of the light absorbing layer and at least one insulating piece, arranged at a location corresponding to the light absorbing piece; forming light-emitting layers on the exposed portion of the first electrodes to cover the second opening portion, and forming second electrodes on the light-emitting layer in a perpendicular direction to the first electrodes.
The preferred embodiment of the present invention provides a method for manufacturing an organic EL device, including steps of forming first electrodes spaced apart from and parallel to each other on a top surface of a first transparent substrate and forming an insulating layer having a first opening portion for exposing a portion of the first electrodes and at least one insulating piece formed in the first opening portion, forming light-emitting layers on the exposed portion of the first electrodes to cover the first opening portion of the insulating layer, forming second electrodes on the light-emitting layer in a perpendicular direction to the first electrodes, and attaching a light absorbing unit on a bottom surface of the transparent substrate, the light absorbing unit having a second opening portion formed at a location corresponding to the first opening portion of the insulating layer and at least one light absorbing piece formed at a location corresponding to the insulating piece of the insulating layer.